Marine conductor pipe connecting method



March 31, 1970 p DODD ET AL 3,503,442

MARINE CONDUCTOR PIPE CONNECTING METHOD Filed July 31, 1968 2 Sheets-Sheet 1 INVENTORSI PAUL L. DODD CHARLES P. PETERMAN WILLIAM H. PETERSEN THEIR ATTORNEY March 31, 1970 p, DODD ET AL 3,503,442

MARINE CONDUCTOR PIPE CONNECTING METHOD Filed July I51. 1968 2 Sheets-Sheet 2 INVENTORSI PAUL L. DODD CHARLES P. PETERMAN WILLIAM H. PETERSEN BY:

THEIR ATTORNEY United States Patent 3,503,442 MARINE CONDUCTOR PIPE CONNECTING METHOD Paul L. Dodd, Mctairie, La., and Charles P. Peterman and William H. Petersen, Houston, Tex., assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed July 31, 1968, Ser. No. 749,195 Int. Cl. E211) 33/035 US. Cl. 166-5 Claims ABSTRACT OF THE DISCLOSURE A method of connecting a marine conductor pipe to an underwater wellhead assembly including the steps of remotely attaching a mono-guideline to a wellhead assembly, lowering marine conductor pipe means and guideline attaching means along the mono-guideline and pulling both of said means into operative engagement with the wellhead assembly.

This invention relates to offshore well operations and pertains more particularly to a method of connecting a marine conductor pipe to an underwater wellhead assembly positioned anywhere from 100 to 1,500 ft. or more below the surface of a body of water.

In an attempt to locate new oil fields an increasing amount of well drilling has been conducted at offshore locations, such for example, as off the coast of Louisiana, Texas and California. As a general rule, the strings of casing in a well, together with the tubing strings or string, extend to a point above the surface of the water where they are closed in a conventional manner that is used on land wells, with a conventional wellhead assembly being attached to the top of the casing. Recently, methods and apparatus have been developed for drilling and completing wells wherein both the well casinghead, and subsequently the wellhead assembly and easing closure device, are located under water at a depth sufiicient to allow ships to pass over them. Preferably, the casinghead and the wellhead closure assemblies are located close to the ocean floor.

It is, of course, necessary to periodically perform workover or maintenance operations with respect to an underwater well and associated wellhead assembly. For this purpose, communication, as by means of a marine conductor pipe, is established between a floating workover vessel and the underwater well so that the desired operations may be carried out therebetween. Alternatively, or in addition to the work to be performed on the well itself, at least a portion of the wellhead assembly may be removed to the surface of the water for maintenance operations. Special wellhead assemblies have been designed and constructed for this purpose. One underwater wellhead structure of this type is shown and described in US. Patent No. 3,064,735, issued Nov. 1962, to R. J. Bauer et al.

For establishing communication between a workover vessel and an underwater well structure for the abovenoted purposes, guideline means are sometimes employed. The guidelines or cables may be permanently attached to the underwater structure and secured at their other ends to a buoy floating on the surface of the water. Alternatively, they may be dropped to the ocean floor from which they are subsequently recoverd by means of grappling hooks or other suitable means.

Cables lying on the ocean floor tend to become entangled with each other and with the wellhead assembly, and guide cables attached to a floating buoy also have a tendency to become entangled as well as constitute a 3,503,442 Patented Mar. 31, 1970 hazard to sea trafiic. In an attempt to avoid these difiiculties, buoy line housing and release means have sometimes been incorporated in wellhead assembly constructions whereby a buoy line may be released from the housing to extend to the surface of the water upon application of power through a supply line or upon an electrical signal transmitted from a vessel. Also, acoustic releasing devices have been used for this purpose. In such arrangements there is always the possibility that the buoy line may become fouled or that the hostile sea water environment may render the buoy line release mechanism inoperative.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved method for remotely locating an underwater wellhead assembly installing guide lines thereon, and making a connection between the wellhead assembly and a marine conductor pipe.

A further object of the present invention is to provide a method for remotely attaching a marine conductor pipe to a wellhead assembly wherein the sea water environment will have no adverse effect in the proper performance thereof.

These objects have been attained in the present invention by providing a method of remotely establishing contact with an underwater wellhead assembly from a floating vessel and of connecting a marine conductor pipe and guideline means to the assembly. The method includes the steps of remotely attaching a mono-guideline between the vessel and the assembly, and lowering a marine conductor pipe having connector means along the mono-guideline into position on the assembly. Substantially simultaneously with the lowering of the marine conductor pipe, guideline carrying means is lowered from the vessel into engagement with the assembly.

DESCRIPTION OF THE DRAWING These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE 1 is a diagrammatic view taken on longitudinal projection illustrating a mono-guideline being lowered from a floating vessel positioned on the surface of the ocean to the proximate vicinity of a wellhead assembly on the ocean floor;

FIGURE 2 is a diagrammatic view taken on longitudinal projection illustrating a mono-guideline connected between a floating vessel and a wellhead assembly;

FIGURE 3 is a diagrammatic view taken on longitudinal projection illustrating a marine conductor pipe connector and guideline connecting assembly being lowered onto a wellhead assembly along a mono-guideline;

FIGURE 4 is a diagrammatic view taken on longitudinal projection illustrating a portion of the marine conductor pipe connector and guideline connecting assembly of FIGURE 3 in contact with a portion of the wellhead assembly; and

FIGURE 5 is a diagrammatic view taken on longitudinal projection illustrating the marine conductor pipe connector and guideline connecting assembly of FIG- URES 4 and 5 in complete operative engagement with the wellhead assembly.

Referring to FIGURE 1 of the drawing, a drilling vessel or platform 11, of any suitable floatable type is illustrated as floating on the surface of a body .of water 12 and substantially fixedly positioned over a preselected location by suitable barge positioning means or by being anchored to the ocean floor 13 by suitable anchors (not shown) connected to the anchor lines 14 and 15. Equipment of this type may be used when carrying on well operations in water depths varying from about to 1500 feet or more. The vessel 11 is equipped with a suitable derrick 16 as well as other auxiliary equipment needed during the drilling of a well. The derrick 16 may be either centrally located on the vessel or extend in from one edge, but in any event the lower end thereof is positioned in such a manner as to have unrestricted access to the body of water 12. Additionally, it is to be understood that the method according to the present invention may be carried out with equal facility from any suitable operational base positioned above the surface of the water such, for example, as from a drilling platform having feet extending to the ocean floor or from a platform permanently positioned on the ocean floor.

A typical underwater wellhead structure is illustrated in FIGURE 1 as comprising a base member 17 which is positioned on or near the ocean floor 13 and is fixedly secured to a conductor pipe or large diameter well casing 18 which extends down into a well, which has been previously partially drilled, and is preferably cemented therein. The base base member 17 supports two or more vertically-extending guide columns 19 and 20. An upstanding wellhead assembly 21 is mounted on base member 17 and communicates with well casing 18 in the usual manner. The wellhead assembly includes a wellhead connector 22 and a blowout preventer stack 23. The blowout preventers comprising stack 23 may be either hydraulically, pneumatically, or electrically actuatable. The wellhead assembly terminates at its upper end with a reentry conduit 24 which supports a frame 25 having a mono-post 26 mounted thereon. Preferably, reentry conduit 24 has a closure cap 27 releasably engaged thereon to protect the interior of the assembly from the possibly harmful effects of the sea water.

Depending from vessel 11 by means of a pipe string 27 is mono-guideline attachment means 28. Mono-guideline attachment means 28 includes a television camera 29 and a 'sonar unit 30, the purposes of which will be described in greater detail below. Further included in mono-guideline attachment means 28 is a mono-guideline support fixture 30a having a cone-shaped lower portion 31 as shown. A mono-guideline attachment means of the type illustrated is described more full in copending US. Patent application Ser. No. 749,171, filed July 31, 1968. Since any suitable mono-guideline attachment means may be used in carrying out the method of the present invention and the illustrated mono-guideline attachment means is described in detail in the above-identified copending patent application, it will not be further described here. Sufiice it to say that a mono-guideline latching mechanism (not shown) connected to mono-guideline 32 is releasably retained in support fixture 30a. The latching mechanism may be of any suitable type such as that described in US. Patent No. 3,050,140, issued Aug. 21, 1962, to W. J. Hayes.

The mono-guideline 32 extends upwardly along pipe string 27 to vessel 11 where it is yieldably retained under tension by suitable tension means on vessel 11. The tensioning means may be of any known type but preferably comprises a portion of a wave cancellation mechanism indicated generally by numeral 33. One suitable tensioning means and wave cancellation mechanism which may be used for this purpose is disclosed in co-pending U.S. application Ser. No. 732,916, filed May 29, 1968, but it is to be understood that any suitable tensioning means may be utilized according to the requirements of practice.

The operation of attaching mono-guideline 32 to the wellhead assembly is as follows. The vessel 11 is positioned over the approximate vicinity of the wellhead assembly and suitably anchored or otherwise substantially fixedly positioned. The mono-guideline attachment means 28 and associated mono-guideline 32 are then lowered from vessel 11 by means of pipe string 27. This is accomplished by lengthening pipe string 27 through the addition of additional pipe sections in the usual manner until it is determined that the pipe string is of sufiicient length to position mono-guideline attachment means 28 at a distance from ocean floor 13 slightly greater than the height of the wellhead structure to be operatively engaged. At this point, the sonar unit 30 and television camera unit 29 are actuated, both of said units being monitored by an operator on vessel 11 in the usual manner. The pipe string is manipulated until the operator observes that cone-shaped lower portion 31 of mono-guideline attachment means 28 is positioned over mono-post 26 of the wellhead assembly. The manipulation of pipe string 27 may be carried out through the use of a water jet 34 the direction of which may be controlled from the vessel. After placement of cone-shaped lower portion 31 over mono-post 26, the pipe string 27 is then further lowered from vessel 11 until the cone-shaped lower portion is seated on the mono-post. As is more fully disclosed in the above-mentioned US. application Ser. No. 749,195, the mono-guideline latching mechanism (not shown) which is retained in support fixture 30a latches onto monopost 26 to attach mono-guideline 32 thereto, The monoguideline attachment means 28 is then withdrawn to vessel 11 by pipe string 27 thus leaving the mono-guideline 32 connected to mono-post 26 as shown in FIGURE 2. It may be desirable to incorporate in mono-guideline attachment means 28 a suitable mechanism to remove the closure cap 27 from reentry conduit 24 at the time monoguideline attachment means 28 is withdrawn to the vessel 11 by means of pipe string 27. A mechanism of this type is disclosed more fully in copending US. application Ser. No. 749,171, filed July 31, 1968.

Referring now to FIGURE 3 of the drawing, a connector assembly including a wellhead connector 41 is lowered from vessel 11 by means of a marine conductor pipe 42 after having been operatively affixed thereto by coupling member 43. As with pipe string 27, the lowering operation is carried out through the addition of individual sections to the conductor pipe. The conductor pipe is held at its upper end by any suitable adjustable tensioner means such as hydraulic tensioner unit 44. As the conductor pipe 42 is gradually lengthened, the wellhead connector 41 is guided along mono-guideline 32 by means of a tubular element 45 also comprising a portion of the connector assembly and frame-mounted on connector 41. Tubular element 45 defines a throughbore (not shown) through which mono-guideline 32 passes freely. Also frame-mounted on connector 41 and comprising a portion of the connector assembly are cylindrical elements 46 and 47 which house therein latch members 48 and 49, respectively. Latch members 48 and 49 are connected to guidelines or guidecables 50 and 51 as shown and are normally releasably retained relative to guideline carrying means comprising cylindrical elements 46 and 47 as shown in FIGURE 3 by lock members (not shown). The guidelines 50 and 51 extend to vessel 11 and are supported thereby in any known manner. For additional details concerning a cylindrical element and latch member arrangement similar to that illustrated herein and which is suitable for use in practicing the method according to the present invention, reference may be had to copending US. Patent application Ser. No. 731,382, filed May, 23, 1968.

Referring now to FIGURE 4 of the drawing, the procedure for bringing the wellhead connector and related structure into engagement with the wellhead assembly 21 is as follows. As previously stated, hydraulic tensioner unit 44 normally urges conductor pipe 42 in an upward direction. As may be seen with reference to copending US. application Ser. No. 732,916, filed May 29, 1968, the upward directed force normally exerted by a unit of this type is greater than the combined weight of the marine conductor pipe 42, wellhead connector 41 and said guideline carrying means. Therefore, in an arrangement of this sort it is necessary to overcome the upwardly directed force of hydraulic tensioner unit 44 so that the conductor pipe and depending structure will be pulled down into operative engagement with wellhead assembly 21. One arrangement for accomplishing this is also shown in US.

application Ser. No. 732,916. This arrangement is illustrated in schematic fashion in FIGURE 4 wherein a pulldown line 52 is attached to marine conductor pipe 42, passes under a sheave means 53 rotatably mounted in suitable fashion on mono-guideline 32, and thence proceeds upwardly to wave cancellation mechanism 33. It is to be understood that the pull-down line 52 is then suitably end-connected to a hoist 54 mounted on vessel 11 whereby actuation of the hoist 54 will pull downwardly marine conductor pipe 42 in a manner obvious from review of the drawing. Since the pull-down line 52 and its connection to the various related elements, such as wave cancellation mechanism 33 is not essential in the carrying out of the method according to the present invention and is described in detail in the above copending application Ser. No. 732.916. it will not be described further here.

The marine conductor pipe 42 is pulled downwardly until tubular element 45 is pulled onto mono-post 26 with the mono-post extending into the throughbore (not shown) defined by the tubular element. It is also desirable to provide cooperating orienting means on the mono-post 26 and the tubular element 45 to selectively rotatably orient the connector assembly to a predetermined position wherein the latch members 48 and 49 are positioned over guide columns 19 and 20 for the purpose which will be more fully brought out below. Once again, reference may be had to copending U.S. application Ser. No. 731,382, for more detailed information relating to a cooperating connector assembly and wellhead assembly which are suitable for use in practicing the method according to the present invention. As is more fully described in U.S. application Ser. No. 731,382, a latching mechanism (not shown) is disposed within the throughbore defined by tubular element 45 which engages a cooperating portion of mono-post 26 to prevent the tubular element from being axially removed from the mono-post. After the latching mechanism (not shown) disposed within the tubular element throughbore is actuated and the above-noted orienting means (not shown) have rotatably positioned the connector assembly to a predetermined position, the cooperating elements of the marine conductor pipe 42, the wellhead assembly 21 and the connector assembly 22 will be as shown in FIGURE 4. Although the latching mechanism (not shown) disposed within the tubular element throughbore will prevent tubular element 45 from being axially removed from mono-post 26, the connector assembly is still freely additionally movable to the position illustrated in FIGURE 5. This additional movement may be initiated by either simply continuing to pull marine conductor pipe 42 downwardly by pull-down line 52 or through the use of hydraulic final pull-down cylinders of the type disclosed in copending U.S. Patent application Ser. No. 731,495, filed May 23, 1968. This latter approach may be desirable if great control is needed but, in any event, after the connector assembly has been positioned as shown in FIG- URE 5 the wellhead connector 41 is positioned in operative engagement with wellhead assembly reentry conduit 24 so that the desired underwater operations may be porformed from vessel 11 through conductor pipe 42.

Subsequent to the positioning of wellhead connector 41 in operative engagement with reentry conduit 24, the latch members 48 and 49 are dropped onto guide columns 19 and 20 by releasing the lock members (not shown) cooperating with cylindrical elements 46 and 47. With this operation, guidelines 50 and 51 are attached to guide columns 19' and 20 so that auxiliary equipment may be run to wellhead assembly 21 as desired or all or a portion of either the wellhead assembly itself or the connector assembly may be readily returned to vessel 11.

We claim as our invention:

1. A method of remotely establishing contact with an underwater wellhead assembly from a vessel floating on a body of water and of connecting a marine conductor pipe and guideline means to said wellhead assembly, said method comprising:

lowering mono-guideline attachment means from the vessel by means of a pipe string, said mono-guideline attachment means carrying one end of a mono-guideline extending to said vessel;

positioning said mono-guideline attachment means over said wellhead assembly;

further lowering said mono-guideline attachment means 'until it operatively engages said wellhead assembly; attaching said mono-guideline to said wellhead assembly; withdrawing said mono-guideline attachment means to said vessel by said pipe string while leaving said mono-guideline secured to said wellhead assembly;

lowering along said mono-guideline to said wellhead assembly a marine conductor pipe having connector means at the lower end thereof;

lowering guideline carrying means from the vessel to the proximate vicinity of the wellhead assembly substantially simultaneously with the lowering of the marine conductor pipe; bringing said lower end of said marine conductor pipe into operative engagement with said wellhead assembly;

lowering said guideline carrying means from the proximate vicinity of the wellhead assembly into engagement with the wellhead assembly; and

connecting guideline means carried by said guideline carrying means ,to said wellhead assembly.

2. The method of claim 1 including the steps of applying upward force to said marine conductor pipe prior to its operative engagement with the wellhead assembly, said upward force being slightly greater than the combined weight of said conductor pipe, said connector means and said guideline carrying means; and

subsequently applying sufiicient downward force to said conductor pipe to overcome the upward force imparted to the conductor pipe thereby pulling the conductor pipe into operative engagement with said wellhead assembly.

3. The method of claim 1 including the step of opening a portion of the wellhead assembly substantially simultaneously with the step of withdrawing the mono-guideline attachment means to the vessel by the pipe string.

4. The method of claim 1 wherein the step of bringing the marine conductor pipe into operative engagement with the wellhead assembly comprises interrupting the lowering of the marine conductor pipe from the vessel, axially positioning the marine conductor pipe over the wellhead assembly and further lowering the marine conductor pipe into position on the wellhead assembly.

5. The method of claim 4 wherein the marine conductor pipe and connector means are rotatably oriented with respect to said wellhead assembly as said marine conductor pipe is further lowered into position on the wellhead assembly.

References Cited UNITED STATES PATENTS 2,984,308 5/1961 Bauer et al 7 3,050,140 8/1962 Hayes 166.6 3,166,123 1/1965 Watkins 166-.6 3,179,176 4/1965 Goepfert 166-.6 3,302,709 2/1967 Postlewaite 175-7 X DAVID H. BROWN, Primary Examiner R. E. FAVREAU, Assistant Examiner U.S. C1. X.R. 1757 

